Initial ViewPager support (WIP)

Support for tab-swiping using a ViewPager
Transitioned tabs from Activities to Fragments (from the support library)
Removed intent passing to tabs as they are now fragments
Fix typo in drawable name
MyTabListener: ViewPager tab listener class
CardsFragment: Refactoring and restructuring
Some other general code cleanup and improvements, including try-catch
 optimisations.
Moved the commit countdown to start closer to when the request is made.

TODO: After changing the gerrit source and using up navigation back from
 preferences, FC due to widgets not being attached to window.
Merge change timer start with fixes for refreshing when gerrit changes.

This completes the initial ViewPager support implementation.

Conflicts:
	src/com/jbirdvegas/mgerrit/CardsFragment.java
	src/com/jbirdvegas/mgerrit/GerritControllerActivity.java